1. Field of the Invention
The present invention relates to a battery connection system for use in an electric bicycle and more particularly, to a battery connection system capable of connecting different types of battery for an electric bicycle.
2. Description of the Related Art
Following fast development of battery technology, many different batteries such as nickel-cadmium battery, nickel-metal hydride (NiMH) battery, Li-ion battery and other solid batteries have been continuously developed. Commercial batteries are generally divided into two types, namely, the first-type batteries containing a micro control unit (MCU) therein and the second-type batteries without installation of the micro control unit. These first-type batteries and the second-type batteries have different power supply ability, different control designs and different dimensions to match different circuit designs. In consequence, the battery circuit design for electric bicycle is complicated. Nowadays, many people use bicycles as a personal transportation vehicle. Therefore, there is a big market demand for electric bicycle. Under this market demand, first-type/second-type battery option and peripheral techniques are important.
A first-type battery, for example, Li-ion battery can be discharged and charged repeatedly. Because of the advantage of high energy density, a first-type battery is very suitable for use in an electric bicycle. Further, the internal micro control unit (MCU) of a first-type battery allows integration of peripheral functions in a single chip. Further, the internal MCU of a first-type battery can cooperate with inter-integrated circuit (I2C) technique to provide an electric bicycle with a diversity of power supply. Therefore, using the first-type battery is the best choice for electric bicycle.
However, using a first-type battery in an electric bicycle has drawbacks as follows:
1. The cost of a first-type battery is high. An electric bicycle using a first-type battery will encounter the challenge of market acceptability.
2. The maintenance of a first-type battery is complicated. It is not economic to prepare a spare first-type battery for replacement.
A second-type battery is a traditional low-cost battery with weak electric energy and without any micro control unit built inside. Rechargeable NiMH battery is the most commonly seen second-type battery. A second-type battery for bicycle is normally packed in a battery box and installed in the bicycle frame beneath the rear luggage carrier or saddle. Further, a second-type batter is replaceable. However, a second-type battery has the drawbacks as follows:
1. The energy density (wh/kg) of a second-type battery is much lower than a first-type battery of same weight; the energy density (wh/l) of a second-type battery is much lower than a first-type battery of same volume. Low power supply density is the major drawback of a second-type battery.
2. A second-type battery has a short cycle lifetime, and the problem of self-discharging instability.
Regular electric bicycles are compatible to one type of battery only, i.e., they do not allow selective use of a first-type battery or a second-type battery.
Therefore, it is desirable to provide a bicycle battery connection system, which allows an electric bicycle to use one of a first-type battery having an MCU therein and a second-type battery without an MCU selectively.